1. Field of the Invention
The present invention relates to an apparatus and a method for repairing an anatomic vessel wall or the wall of a hollow organ, such as the esophagus, particularly in the human body. In particular, the present invention relates to an attaching or locking element for attaching an implant, such as stent or stent graft, to a vascular or hollow organ wall from the outside of the wall, as well as an instrument for positioning and inserting the attaching or locking element into the body. The present invention also encompasses a method for attaching or locking an implant to a vessel or hollow organ wall.
2. Description of Related Art
An Abdominal Aortic Aneurysm (xe2x80x9cAAAxe2x80x9d) is a weakening of the wall of the aorta in the abdominal area. AAAs pose a significant health problem and over 160,000 AAAs are diagnosed annually in the United States. A full 25% of AAAs will go on to eventually rupture; in spite of numerous advances in acute medical care, medical transport and resuscitation, ruptured AAAs continue to have a 50% mortality rate.
FIG. 1 shows an infrarenal AAA Axe2x80x2 located in the torso T of a patient P, below the heart H and kidneys K and above the point of bifurcation B of the aorta A into the iliac arteries IA. As may be seen by comparing FIGS. 2 and 3, a normal aorta A (FIG. 2) exhibits non-bulging walls above the point of bifurcation B, while an aorta A which includes an AAA Axe2x80x2 (FIG. 3) bulges outwardly from its normal condition. This bulging is the result of weakening of the aortic vessel walls.
The traditional surgical technique for treating AAAs involved excision of the aneurytic tissue and replacing that tissue with either a synthetic graft or a graft from another section of the patient""s body. This approach required a large abdominal incision and total bowel displacement and large disruption of the retroperitoneum, followed by excision of the aneurytic tissue and attachment of the replacement graft to the vessel ends. Disadvantages of this prior art surgical technique include hypothermia, coagulation problems, prolonged ileus, a risk of sexual disfunction and significant pain and disfigurement. As a result of these significant disadvantages attendant to the traditional surgical technique, alternative techniques for AAA repair have been investigated and used.
In 1992, Juan Parodi, a surgeon, first described the placement of a percutaneous vascular prosthesis or stent in the abdominal aorta using interventional radiological techniques in Transfemoral Intraluminal Graft Implantation for Abdominal Aortic Aneurysms, Ann. Vasc. Surg. 1991: 5:491-499. The prosthesis or stent effectively excluded, i.e., provided support for, the aneurysm sac, while avoiding a major access incision in the abdomen. This prior art technique required only a small groin incision, through which the stent was inserted and lead to the aneurysm site with appropriate stent guidance and deployment tools. Upon reaching the aneurysm site, the stent was deployed and grafted to the vascular walls of the aorta at the aneurysm site. A stent S deployed at an aneurysm Axe2x80x2 is shown in dotted lines in FIG. 3. The use of stent grafts, as in this prior art technique, decreased patient morbidity, and because of the less invasive nature of the technique used to insert and deploy the graft, significantly reduced the problems with the traditional surgical technique for repairing AAAs.
Despite the advantages attendant the stent graft technique, difficulties in passing the stent to the aneurysm site, untimely opening of the stent, and complications, including emboli at the proximal and distal ends of the aneurysm, intimal damage, perforation, and thrombosis, have occurred. In addition, unsatisfactory methods and devices for proximal stent end fixation in order to prevent stent migration, as well as persistent endoleaks, have limited the effectiveness of stent grafts. The proximal stent end is the end of the stent nearest to the heart; this end needs to be fixed to the aorta in order to prevent the stent from migrating from its initial deployed position to a position where it does not fully exclude and support the AAA. This movement or migration can also cause endoleaks (L, FIG. 3), in which blood passes between the stent S and the aneurysm Axe2x80x2, putting pressure on the aneurysm which can result in rupture.
When inserting implants, such as stents or stent grafts, into vessels or hollow organs, in particular when repairing an aneurysm using a stent graft, it is necessary that the stent introduced into the vessel or hollow organ be attached at both its distal and proximal ends tightly and permanently to the vessel wall surrounding the stent, in order to ensure that the stent does not migrate in the vessel and to ensure that the stent seals off the aneurysm, thus reinforcing the weakness in the vessel. Prior art stents used for repair of AAAs have used a variety of mechanisms for attaching the stent to the vessel wall. One mechanism used to attach a stent to a vessel wall is hook-shaped projections at the proximal and distal ends of the stent, which hook-shaped projections are pressed against the vascular wall from the inside of the vessel. The hook-shaped projections mechanically grip the vessel walls to secure the stent or stent graft to the vessel wall. In a similar attachment method, disclosed in U.S. Pat. No. 5,527,355, the stent or stent graft is secured in position against the vessel wall from the inside using hook-shaped retaining elements; these hook-shaped retaining elements are inserted into bands and surround the vessel externally.
PCT Publication No. WO 97/09008 to Medtronics shows a tubular implant used for repairing aneurysms. In this implant, a sealing layer is disposed at least at the ends of the implant, in order to reduce endoleaks. The implant described in this publication, however, does not include any mechanism for securely fastening the implant to the vessel wall to prevent migration.
U.S. Pat. No. 5,342,393 to Richard Stack of Duke University shows a device for repairing a perforation in a vascular wall. The device of that patent is not disclosed for any use in securing implants into an anatomic vessel or hollow organ. Furthermore, the device of that patent uses a large-diameter catheter or sheath which is inserted through a large perforation in the vessel wall. This device is therefore not suitable for securing an implant to a vessel or hollow organ wall, where large perforations are to be avoided in deploying the implant.
U.S. Pat. No. 4,669,473 to Acufex Microsurgical describes a surgical fastener used for fastening two or more sections of tissue to one another. This fastener is not disclosed or used for fastening of any type of anatomic vessel or organ, in particular any type of hollow anatomic vessel or organ, and the thick bar-like head of that fastener is specifically designed to be embedded within the tissue to be fastened. The head of the fastener also includes at least one pointed end for embedding in tissue. Furthermore, the fastener of that device is not used to clamp two walls together, nor is that fastener used to attach an implant to a vessel or hollow organ.
Prior art methods for affixing an implant, such as a stent or stent graft, to a vessel or hollow organ wall have not always been reliable. In addition, many of these prior art methods could only be employed using open surgical techniques requiring large incisions. These prior art methods, and the apparatuses used with these methods, have not been amenable to less-invasive techniques.
An object of the present invention is to provide an attachment or locking apparatus which can effectively secure an implant, such as a stent or stent graft, to a vessel or hollow organ wall and which allows less invasive techniques, such as laparotomy with a markedly reduced incision, and minimally-invasive techniques, such as laparoscopy or endoscopy, to be used to attach the implant.
A further object of the invention is to provide a method and device for deploying an attachment or locking apparatus for securing an implant, such as a stent or stent graft, to a vessel or hollow organ wall which achieves minimal yet reliable penetration of the vessel or hollow organ wall, as well as a method or device for manipulating the attaching or locking apparatus in the body.
A still further object of the invention is to provide an attachment or locking apparatus and a method and device for deploying the apparatus for fixation of a stent graft to a the wall of the aorta in the repair of AAAs which prevents stent migration and persistent endoleaks.
These and other objects of the present invention are achieved using a locking element which is inserted through the vessel or hollow organ wall and the implant from the outside of the vessel or hollow organ wall. The stent lock of the present invention preferably includes a thin retaining element. The retaining element has a clamping element joined flexibly at one end of the retaining element. A fixing element is secured in position on the retaining element to secure or attach the implant in place.
In, for example, the attachment of a stent or stent graft to a vascular wall, a thin cannula may be inserted into the patient""s body, such that the cannula penetrates both the vascular wall and the stent or stent graft inserted within the vascular wall. The retaining element may then be inserted through the cannula so that the end with the clamping element is deployed on the inside of the stent or stent graft, and the other end projects through the stent or stent graft and the vessel wall. When withdrawing the end of the retaining element opposite the clamping element from the vessel, the clamping element, because of the flexible connection to the retaining element, tilts into a position transverse to the insertion opening. As a result, the clamping element is positioned against the inner wall of the stent or stent graft, so that the clamping element abuts against the interior of the vessel and the implant. The fixing element, already placed upon the retaining element or attachable upon the retaining element, is pushed from the outside against the vascular wall. In this manner, the distal and proximal ends of the stent or stent graft are locked together with the vessel wall and the stent or stent graft and the vessel wall are held between the clamping element and the fixing element. The fixing element can be fixed in position on the clamping element, after providing the necessary tension in both the stent or stent graft and the retaining element, by crimping or deformation, for example, or by a snap fit.
It is particularly advantageous if the clamping element is connected to the retaining element in the mid-section of the clamping element, so that when the retaining element is withdrawn from the opening in the vessel or hollow organ wall, the clamping element is positioned on both sides of the opening in the vessel or hollow organ wall across an equal contact area of the implant.
The clamping element must be designed so that it is insertable through a very small opening in the vessel or hollow organ wall and deployable into the interior of the vessel or hollow organ, and so that in the interior thereof, it nevertheless lies over a sufficiently large area against the implant so that the clamping element is reliably prevented from being withdrawn again through the opening in the wall. This can be ensured, for example, by the manner in which the clamping element is introduced into the interior of the vessel or hollow organ. The clamping element may be folded, bent or rolled into an elongated shape and inserted into the vessel or hollow organ, and thereafter may open, flex or expand therein. In a particularly preferred specific embodiment the clamping element may be pin-shaped. Thus, it becomes possible to insert the clamping element in the longitudinal direction of the cannula, with a very small cross-sectional puncture area, into the interior of the vessel or hollow organ. Once in the vessel or hollow organ, the clamping element flexes or spreads out into a transverse position, in front of the insertion opening, and thus prevents the clamping element from pulling out of the insertion opening. It is advantageous if the clamping element flexes or expands out radially from the retaining element, in a plane transverse to the longitudinal direction of the retaining element, thus providing a suitable contact area for the clamping element against the implant. The clamping element and retaining element may be integrally formed, or the retaining element may be embedded into, or otherwise connected to, the clamping element.
In one preferred embodiment, the clamping element can be curved in its transverse direction, so that it adapts or fits to the curve or shape of the implant or vessel or hollow organ wall. The clamping element preferably has ends which are not sharp, and may be smooth, preventing the ends of the clamping element from piercing or penetrating the vessel or hollow organ wall, thereby preventing damage.
One particularly preferred specific embodiment provides for the retaining element and the clamping element to be formed in one integral piece. The flexible joining of these two parts is then effected, for example, by manufacturing the retaining element and the clamping element integrally from a suitable polymeric or metallic material.
In another specific embodiment, the clamping element is tubular, and the retaining element is formed by a suture or thread whose two ends are introduced from opposite sides into the tubular clamping element and emerge together from the clamping element through the opening in the vessel or hollow organ wall.
It is beneficial if the fixing element is a permanently compressible sleeve through which the retaining element is passed. Initially, this sleeve is freely movable or slidable on the length of the retaining element. The fixing element can be brought forward closely against the outside of the vessel or hollow organ wall so that the wall and the implant, such as a stent or stent graft, are sufficiently compressed between the clamping element and the fixing element. When this condition is reached, the sleeve is crimped or deformed and thus secured in position with respect to the clamping element. As an alternative, the fixing element may be made of a resilient material, and may be snapped into an appropriate position using beads or other protuberances along the length of the retaining element.
At an end of the retaining element opposite the clamping element, an enlargement can be provided which prevents the fixing element, when it is not yet secured in position, from sliding off the retaining element. This feature prevents the fixing element from dislodging from the retaining element during the insertion procedure.
In another preferred specific embodiment, a pressure element, having a pressure surface which is arranged approximately transverse to the longitudinal direction of the retaining element and approximately parallel to the clamping element, is supported on the retaining element between the vessel or hollow organ wall and the fixing element. The pressure element preferably is freely movable along the retaining element. In particular, this pressure element can be a disk or band having a center through which the retaining element is passed. This pressure element is held by the fixing element against the outside of the vessel or hollow organ wall, and ensures that the force holding the vessel or hollow organ and the implant together is introduced over a large surface area on the outside of the vessel or hollow organ.
In addition, between the pressure element and the vessel or hollow organ wall, a large-area pressure-distribution element can be supported on the retaining element in a manner that it is moveable during insertion. This pressure-distribution element further distributes the pressure against the vessel or hollow organ wall. It is advantageous if the pressure-distribution element is elastically compressible, so that it positions itself over a large surface area against the vessel or hollow organ wall, thus reducing pressure peaks on the wall. In one preferred embodiment, the pressure-distribution element can have the shape of a cylinder, and the retaining element may pass transversely through the pressure-distribution element.
The individual parts of the locking element are made of materials well tolerated by the body, in particular the retaining element, the clamping element, the fixing element, the pressure element and/or the pressure-distribution element can be made of a non-absorbable plastic material. In other embodiments, it is also possible for the retaining element, the fixing element and/or the pressure element to be made of titanium, or possibly of another metal alloy well tolerated by the body.
In another preferred specific embodiment of the invention, the pressure-distribution element can be made of a foam or a non-woven fabric, so that it is elastically compressible and positions itself gently against the outer surface of the vessel or hollow organ wall.
It is also the object of the invention to provide a positioning or insertion instrument for inserting and locking in place the locking element of the present invention. This objective is fulfilled according to the present invention by a positioning instrument that includes a hollow needle, trocar or cannula into which at least the clamping element of the locking element is insertable, and an ejector to push the locking element out of the hollow needle, trocar or cannula. This apparatus may be large enough to be manipulable outside the body, or may be made to be inserted within the body so as to manipulable using appropriate endoscopic tools. Using such a positioning instrument, the locking element is accommodated in the hollow needle, trocar or cannula which can be inserted into the patient percutaneously, via laparoscopic, laparotomic or endoscopic techniques, and thereafter through the vessel or hollow organ wall and the implant. The clamping element is then pushed out of the hollow needle, trocar or cannula by an ejector. The ejector can extend out of the body cavity, to be actuated by hand by the surgeon, or could be located within the abdominal cavity, to be actuated using suitable endoscopic tools. After withdrawing the hollow needle, trocar or cannula from the vessel or hollow organ, the small opening caused by the hollow needle, trocar closes elastically around the retaining element which projects outwardly through the closed opening. The clamping element may be pressed against the inner wall of the implant by pulling on an opposite end of the retaining element. Thereafter, the pressure-distribution and/or pressure elements may be pressed against the outside of the vessel or hollow organ wall, and then the fixing element secured in place to lock the implant in place.
It is beneficial if the hollow needle, trocar or cannula is beveled at the end inserted into the patient, thereby tapering to a sharp point. It is also advantageous if the hollow needle, trocar or cannula has an elongated slot open toward the end inserted into the patient for receiving the clamping element. This is especially beneficial when the clamping element flexes or expands radially from the retaining element and therefore would be impeded by the inner wall of the hollow needle, trocar.
Depending on the location at which the hollow needle, trocar or cannula is to be inserted into the patient, the hollow needle, trocar or cannula can be optionally straight or curved. The hollow needle, trocar or cannula is preferably very thin, sharp and rigid, so that it may readily penetrate calcified vessel tissue, without creating a large puncture subject to weakening or rupture.
In the method of the present invention, as exemplified by its use in the treatment of an AAA, a first percutaneous incision is made at a location near the aneurysm site. A second percutaneous incision is made preferably in the groin or pubic area, to gain access to a femoral or iliac artery or the distal end of the abdominal aorta. Using standard interventional techniques the stent or stent graft is guided to the aneurysm site and then deployed. Access is gained to the exterior of the aorta at the aneurysm site through the first incision. The first incision may be a laparotomy incision, followed by suitable procedures to gain open access to the aorta, or may be a small incision as part of a laparoscopic procedure in which additional small incisions are made to deploy additional instruments into the abdomen. In either case, the positioning device, with an attached locking element is inserted through the first incision, guided to the aneurysm site, and then the hollow needle, trocar or cannula punctures the outside wall of the aorta and is inserted within the interior of the aorta and the stent or stent graft. The clamping element is then ejected, using an ejector, into the interior of the aorta and stent or stent graft. The hollow needle, trocar is then withdrawn. The locking element is pulled tight, and pressure-distribution and/or pressure elements are then slid down the locking element toward the aorta wall. The fixing element is then slid against the pressure-distribution and/or pressure elements, and secured into place by crimping, deforming, or by a snap fit. The free end of the locking element may then be cut off near the fixing element. The process of inserting and securing the locking element may be repeated until a sufficient number of locking elements are in place to securely hold the stent or stent graft to the aorta wall.